The STC5270 from Connor-Winfield is an integrated single chip solution for the synchronous clock in SDH, SONET, and synchronous Ethernet network elements. The device is fully compliant with ITU-G.813 and Telcordia GR1244 and GR253. The STC5270 accepts 2 reference inputs and generates 2 independent synchronized output clocks. Reference input frequencies are automatically detected. All reference switches are hitless. Synchronized outputs may be programmed for a wide variety of SONET and SDH as well as Synchronous Ethernet frequencies. The clock generator includes a DPLL (Digital Phase-Locked Loop), which may operate in the Freerun, Synchronized, and Holdover modes. A standard SPI bus provides access to the STC5270’s internal control and status registers. The device operates with an external 20 MHz OCXO or TCXO as its MCLK.